Mechanical seals, often times referred to as face seals, are commonly utilized on pumps and the like to provide a seal between a fluid handling device and the surrounding environment. In such mechanical seals, there is typically provided an opposed pair of face rings which have annular faces which are disposed in opposed association, with one ring typically being nonrotatably secured relative to a shaft, and the other nonrotatably secured relative to a surrounding housing. The face rings are urged axially toward one another and may have the opposed faces in relatively rotatable sliding contact with one another, or in some use situations may be separated by a fluid film, such as a gas seal. The face rings are themselves individually retained by surrounding support structures which may be associated with or comprise a part of the housing or shaft. In many instances the face rings are constructed of hard but brittle materials such as tungsten carbide, silicon carbide or other suitable materials which are well known for this utilization. Because of the hard but brittle characteristics of these materials, coupled with the operational requirements of the overall seal assembly, various structures have in the past been utilized for positionally securing the respective face rings.
In one conventional and well known structure, the face ring is positioned within an axially-opening recess formed in a support member which has a shroud-like sleeve which projects axially around the outer periphery of the face ring. A snap ring is releasably engaged within the mouth of the shroud in overlapping relationship with the face ring to axially secure the face ring to the support member. While this arrangement has been utilized in mechanical seals for many years, and does operate satisfactorily in many use situations, nevertheless the overall arrangement does possess undesirable features inasmuch as the utilization of the snap ring does require forming of an internal groove within the shroud, which groove in turn must be accurately formed and positioned so as to provide the overall but rather precise tolerances required with respect to positioning of the face ring on and within the shroud. Further, with this type of securing arrangement, in situations where the seal is subjected to pressure reversals (i.e., the system pressure is applied to the back side of the face ring), the snap ring is normally incapable of guaranteeing proper face ring compression, such as against a secondary seal, and thereby sealability and hence failure can occur. This mounting arrangement is unsuitable for situations where such pressure reversals may occur.
In a further known face ring retainer arrangement, the face ring is itself press fit within the shroud of the support member. This arrangement, however, can cause undesirable internal stresses and distortion of the face ring.
In another known face ring retainer arrangement, particularly in an attempt to overcome the problems associated with pressure reversals on the face ring as discussed above, the shroud has been provided with a separate retainer ring which is welded to the front edge of the shroud in overlapping and hence securing relationship to the face ring. While this arrangement is readily capable of withstanding a pressure reversal situation, nevertheless the overall manufacturing of this arrangement is both costly and complex. Further, this requirement of welding between the shroud and retainer ring, in the vicinity of the face ring when the latter is assembled within the shroud, can result in undesired thermal stresses and distortions.
Of even greater significance with respect to the welded retainer structure of the type described above, is the inability to carry out a simple and inexpensive field or remote location repair or rebuilding of the seal assembly. Replacement of face rings is a repair which is commonly required, and with the welded assembly described above, such repair cannot be easily or economically carried out at the job site or at a typical remote repair location since such location normally does not possess the structure or equipment required for such repair. Replacement of a face ring employing this welded retainer structure typically requires that the assembly be shipped back to the factory for reworking.
A mechanical seal employing a welded retainer structure of the type described above is disclosed in greater detail in U.S. Pat. No. 4,971,337.
Accordingly, this invention relates to an improved face ring retainer arrangement which is believed to overcome many of the disadvantages associated with known arrangements as described above. This improved retainer arrangement is believed highly desirable since it will successfully withstand pressure reversals which may occur in usage, but which in addition will permit the overall seal assembly to be maintained or repaired at the job site or at least at a remote repair location using minimal equipment so as to permit replacement of a face ring, if necessary, without requiring that the seal assembly be returned to the manufacturing site.
More specifically, this improved retainer arrangement is capable of retaining the face ring within the face end of the support ring regardless of whether the seal assembly is pressurized from the inside or outside diameter; and at the same time the secondary seal (e.g. a gasket), which functions as a resilient mounting for the face ring, remains in compression to maintain sealing about the secondary seal.
In the improved seal assembly of this invention, the face ring is disposed within an axially-opening recess associated with a support ring, which support ring includes a sleevelike shroud which externally surrounds the face ring to maintain the face ring in the desired concentric relationship. A separate retainer ring is provided for cooperation between the shroud and face ring to axially and positionally secure the face ring to the support ring. The retainer ring includes an annular ring part which projects radially inwardly so as to radially overlap a part of the exposed face of the face ring to effect axial securement thereof to the support ring. The retainer ring in addition has an axially-extending sleeve part which projects axially and in surrounding relationship to the shroud. This sleeve part has a press-fit engagement with the shroud to create a fixed engagement of the retainer ring to the support ring. This press-fit engagement is capable of withstanding pressure reversals imposed against the rear of the face ring, but allows the retainer ring to be relatively easily removed if necessary without requiring complex tooling or the like so as to permit replacement of the face ring.
In the improved seal assembly, as aforesaid, a secondary seal such as a gasket is preferably resiliently and sealingly engaged between the face and support rings to impose a resilient axial compression force against the face ring.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.